functions-and-operators: remove MySQL Reference Manual links

[dveeden]

First-time contributors' checklist

• I've signed the Contributor License Agreement, which is required for the repository owners to accept my contribution.

What is changed, added or deleted? (Required)

• Remove reference manual links for functions for which we have our own docs.
• Keep links for functions/operators that are not explained in the TiDB docs yet
• We can keep a link at the top linking to the corresponding page in the MySQL Reference Manual like this: TiDB supports most of the user-level [locking functions](https://dev.mysql.com/doc/refman/8.0/en/locking-functions.html) available in MySQL 8.0.

This was done with sed -E -i -e 's/(^#* )\[(.*)\].*$/\1\2/' path/to/file.md

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For details, see tips for choosing the affected versions.

• master (the latest development version)
• v9.0 (TiDB 9.0 versions)
• v8.5 (TiDB 8.5 versions)
• v8.1 (TiDB 8.1 versions)
• v7.5 (TiDB 7.5 versions)
• v7.1 (TiDB 7.1 versions)
• v6.5 (TiDB 6.5 versions)
• v6.1 (TiDB 6.1 versions)
• v5.4 (TiDB 5.4 versions)

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• Other reference link(s):

Do your changes match any of the following descriptions?

• Delete files
• Change aliases
• Need modification after applied to another branch
• Might cause conflicts after applied to another branch

[gemini-code-assist]

Summary of Changes

Hello @dveeden, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the TiDB documentation by streamlining the user experience for functions and operators. It systematically removes direct links to the MySQL Reference Manual for features that are comprehensively documented within TiDB's own pages. This change aims to keep users within the TiDB documentation ecosystem, providing a more cohesive and self-contained information source, while still acknowledging MySQL compatibility where necessary.

Highlights

• Documentation Self-Sufficiency: Removed external MySQL Reference Manual links from numerous function and operator documentation pages where TiDB provides its own comprehensive coverage.
• Improved User Experience: Users will now primarily find information within the TiDB documentation, reducing the need to navigate to external sites for functions already covered.
• Targeted External Links: External links to the MySQL Reference Manual are now maintained only for functions/operators not yet explained in TiDB's own documentation, or for general reference at the top of relevant pages.

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[dveeden]

With this PR:

functions-and-operators/operators.md	75
functions-and-operators/date-and-time-functions.md	62
functions-and-operators/numeric-functions-and-operators.md	38
vector-search/vector-search-functions-and-operators.md	28
functions-and-operators/aggregate-group-by-functions.md	11
tidb-cloud/tidb-cloud-dm-precheck-and-troubleshooting.md	7
scripts/update_mysql_ref.py	7
dm/dm-block-allow-table-lists.md	7
functions-and-operators/string-functions.md	6
functions-and-operators/locking-functions.md	6
functions-and-operators/expressions-pushed-down.md	6
functions-and-operators/control-flow-functions.md	5
character-set-and-collation.md	5
functions-and-operators/cast-functions-and-operators.md	4
dm/dm-glossary.md	4
system-variables.md	3
partitioned-table.md	3
mysql-compatibility.md	3
literal-values.md	3
develop/dev-guide-schema-design-overview.md	3
data-type-string.md	3
data-type-numeric.md	3
vector-search/vector-search-get-started-using-sql.md	2
tidb-lightning/tidb-lightning-data-source.md	2
security-compatibility-with-mysql.md	2
schema-object-names.md	2
releases/release-6.4.0.md	2
functions-and-operators/miscellaneous-functions.md	2
develop/dev-guide-create-table.md	2
user-defined-variables.md	1

And with master:

functions-and-operators/operators.md	75
functions-and-operators/string-functions.md	63
functions-and-operators/date-and-time-functions.md	62
functions-and-operators/numeric-functions-and-operators.md	38
vector-search/vector-search-functions-and-operators.md	28
functions-and-operators/encryption-and-compression-functions.md	13
functions-and-operators/window-functions.md	12
functions-and-operators/json-functions/json-functions-modify.md	11
functions-and-operators/aggregate-group-by-functions.md	11
functions-and-operators/json-functions/json-functions-search.md	9
functions-and-operators/bit-functions-and-operators.md	8
tidb-cloud/tidb-cloud-dm-precheck-and-troubleshooting.md	7
scripts/update_mysql_ref.py	7
dm/dm-block-allow-table-lists.md	7
functions-and-operators/locking-functions.md	6
functions-and-operators/expressions-pushed-down.md	6
functions-and-operators/control-flow-functions.md	5
character-set-and-collation.md	5
functions-and-operators/json-functions/json-functions-return.md	4
functions-and-operators/cast-functions-and-operators.md	4
dm/dm-glossary.md	4
system-variables.md	3
partitioned-table.md	3
mysql-compatibility.md	3
literal-values.md	3
functions-and-operators/json-functions/json-functions-utility.md	3
functions-and-operators/json-functions/json-functions-create.md	3
develop/dev-guide-schema-design-overview.md	3
data-type-string.md	3
data-type-numeric.md	3

[gemini-code-assist]

Code Review

This pull request removes external links to the MySQL Reference Manual from function documentation, which is a good cleanup. My review focuses on ensuring the formatting of the updated headings is consistent with the documentation style guide. I've found several instances in the JSON function documents where function names in headings are missing backticks and have provided suggestions to fix them.

[qiancai]

@dveeden, I've added some MySQL doc links to the Jason function docs. PTAL. Thanks.

3ea7017 (#21821)

[dveeden]

@dveeden, I've added some MySQL doc links to the Jason function docs. PTAL. Thanks.

3ea7017 (#21821)

In general this is ok. But maybe we should consider to put MySQL compatibility info in a separate section in the end of the document instead? The main goal of these documents should be to describe the functionality of TiDB, both for users that migrate from MySQL but also for TiDB users that didn't start with another database.

As JSON was implemented after MariaDB was forked off, there are many differences between MariaDB and MySQL/TiDB. Also note that there is now an official standard: ISO/IEC 19075-6:2021. So in the future we may want to list MySQL, MariaDB and ISO standard compatibility.

For now there is no need to change anything, please keep this as-is.

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2025-11-17 10:42:36.392544269 +0000 UTC m=+1303605.835574138: ☑️ agreed by hfxsd.

[qiancai]

/approve

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: qiancai

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[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-8.5: #22066.